Could 'body clocks' play a role in depression? Study proposes a new 'circadian' subtype

A new study proposes that a distinct subtype of depression, linked to disruptions in the body's internal clock, may play a significant role in the condition. The researchers, led by neuroscientist Emiliana Tonini from the University of Sydney, identified this "circadian depression" subtype in about 2,600 out of over 11,000 participants in the Australian Genetics of Depression Study (AGDS).

Unlike other depressive subtypes defined mainly by symptoms, circadian depression is characterized by a disturbed circadian system. Common antidepressants may not fully address this core feature. The study found that this group was younger, more likely to be female, and reported greater psychological distress, frequent suicidal thoughts, and more physical complaints compared to others. They also experienced weight gain during depressive episodes and symptoms resembling hypomania.

The researchers suggest that treatments targeting the sleep-wake system, such as melatonin or bright light therapy, may benefit those with this subtype. However, further research is needed to determine if circadian disruption is a core biological mechanism in depressed individuals and to assess its impact on treatment outcomes.